1. Field of the Invention
This invention relates to a vacuum chuck apparatus for chucking an article like a plate, box or the like, and more particularly to a vacuum chuck apparatus which has a plurality of suction cups and in which the number of the suction cups to be actually operated is changed according the size of the article to be handled.
2. Description of the Prior Art
There has been known a vacuum chuck apparatus for chucking an article like a plate, box or the like such as a glass plate, a corrugated box or the like. The vacuum chuck apparatus has a plurality of suction cups fixed to a base member such as a chuck frame. The suction cups are pressed against a predetermined surface of the article to be chucked and the air in the suction cups is evacuated to make the pressure in the space surrounded by each suction cup and the predetermined surface of the article, whereby the article is chucked by the vacuum chuck apparatus by suction.
When such a vacuum chuck apparatus is used for transferring articles, the vacuum chuck apparatus should agree with the size of the article. However when separate vacuum chuck apparatuses are prepared for the articles of different sizes, operating cost rises and a large space is required.
Accordingly, it is preferred that a single vacuum chuck apparatus can be used for chucking articles of different sizes. An example of such a "free-size" vacuum chuck apparatus is disclosed in Japanese Utility Model Publication No. 47(1972)-12624. In the free-size vacuum chuck apparatus, a plurality of suction cups are mounted in an array on a chuck frame. The suction cups positioned in the middle of the array are fixed to the chuck frame and are constantly operated irrespective of the size of the article to be chucked, while the suction cups positioned in end portions of the array are mounted on the chuck frame to be movable between an operative position where they can chuck the article by suction together with the fixed suction cups and a retracted position above the operative position. When the size of the article to be chucked is small, the suction cups in the end portions are manually moved to the retracted position and held there by means of engagement members. When the size of the article to be chucked becomes larger, the suction cups in the retracted position are moved to the operative position by manually disengaging the engagement members. Thus, the free-size vacuum chuck apparatus can chuck articles of various sizes.
In a free-size vacuum chuck apparatus disclosed in Japanese Utility Model Publication No. 47(1972)-12625, the suction cups in the end portions of a suction cup array are mounted on the chuck frame to be movable between the operative position and the retracted position above the operative position and at the same time held by arms to be rotatable in a horizontal plane. The movable suction cups are manually swung in the horizontal plane when the size of the article to be chucked changes.
Further, in a free size vacuum chuck apparatus disclosed in Japanese Unexamined Patent Publication No. 4(1992)-41342, each suction cup is supported by a shaft and a pinion is formed on an upper part of the shaft. The pinion is in mesh with a pair of opposed rack members extending in a horizontal direction. The position of the suction cup can be manually changed by pushing up the shaft to disengage the pinion from the rack members, moving the shaft along the rack members and then engaging pinion with the rack members again. By selecting the positions of the respective suction cups according to the size of the article to be chucked, the vacuum chuck apparatus can handle articles of various sizes.
In any of the conventional free-size vacuum chuck apparatus, the suction cups are manually moved when changing the size of the articles to be chucked by the vacuum chuck apparatus, and accordingly, in a line where articles of various sizes are transferred mixed together, the line must be stopped to change the positions of the suction cups every time the size of the article changes, which greatly deteriorates the operating efficiency of the line and makes it impossible to use the vacuum chuck apparatus for an unmanned automated system.